As a bonus action, the will-o'-wisp can target one creature it can see within 5 ft. of it that has 0 hit points and is still alive. The target must succeed on a DC 10 Constitution saving throw against this magic or die. If the target dies, the will-o'-wisp regains 10 (3d6) hit points.

Ephemeral

The will-o'-wisp can't wear or carry anything.

Incorporeal Movement

The will-o'-wisp can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.

Variable Illumination

The will-o'-wisp sheds bright light in a 5- to 20-foot radius and dim light for an additional number of ft. equal to the chosen radius. The will-o'-wisp can alter the radius as a bonus action.